Earth-boring tools for forming wellbores in subterranean earth formations may include a plurality of cutting elements secured to a body. For example, fixed-cutter earth-boring rotary drill bits (also referred to as “drag bits”) include a plurality of cutting elements that are fixedly attached to a bit body of the drill bit. Similarly, roller cone earth-boring rotary drill bits may include cones that are mounted on bearing pins extending from legs of a bit body such that each cone is capable of rotating about the bearing pin on which it is mounted. A plurality of cutting elements may be mounted to each cone of the drill bit.
The cutting elements used in such earth-boring tools often include polycrystalline diamond cutters (often referred to as “PDCs”), which are cutting elements that include a polycrystalline diamond (PCD) material. Such polycrystalline diamond cutting elements are formed by sintering and bonding together relatively small diamond grains or crystals under conditions of high temperature and high pressure in the presence of a catalyst (such as, for example, cobalt, iron, nickel, or alloys and mixtures thereof) to form a layer of polycrystalline diamond material on a cutting element substrate. These processes are often referred to as high-temperature/high-pressure (or “HTHP”) processes. The cutting element substrate may comprise a cermet material (i.e., a ceramic-metal composite material) such as cobalt-cemented tungsten carbide. In such instances, the cobalt (or other catalyst material) in the cutting element substrate may be drawn into the diamond grains or crystals during sintering and serve as a catalyst material for forming a diamond table from the diamond grains or crystals. In other methods, powdered catalyst material may be mixed with the diamond grains or crystals prior to sintering the grains or crystals together in an HTHP process.
PDC cutting elements commonly have a planar, disc-shaped diamond table on an end surface of a cylindrical cemented carbide substrate. Such a PDC cutting element may be mounted to an earth-boring rotary drag bit or other tool using fixed PDC cutting elements in a position and orientation that causes a peripheral edge of the diamond table to scrape against and shear away the surface of the formation being cut as the drill bit is rotated within a wellbore. As the PDC cutting element wears, a so-called “wear scar” or “wear flat” develops that comprises a generally flat surface of the cutting element that ultimately may extend from the front, exposed major surface of the diamond table to the cylindrical lateral side surface of the cemented carbide substrate.
Early PDC cutting elements had relatively thinner diamond tables having an average thickness of about one (1) millimeter or less. As such cutting elements were used to cut formation material, the wear scar that developed often included an uneven profile wherein the surface of the diamond table that was rubbing against the formation projected outward from the cutting element beyond the adjacent surface of the cemented carbide substrate that was rubbing against the formation. It was believed that this phenomenon was due to the fact that the rubbing surface of the cemented carbide substrate was wearing at a faster rate than was the rubbing surface of the diamond table. The portion of the diamond table at the wear scar projecting outward beyond the adjacent rubbing surface of the cemented carbide substrate has been referred to as a “shear lip.” The formation of such a shear lip may beneficially result in an increased rate of penetration (ROP).